污控ch61等离子体1class

1、等离子体等离子体 等离子体是处于电离状态的气体，是美国科学家等离子体是处于电离状态的气体，是美国科学家Langmuir于于1927年在研究低气压下汞蒸汽中放电年在研究低气压下汞蒸汽中放电现象时命名的。现象时命名的。 等离子体由大量的电子、离子、中性原子、激发等离子体由大量的电子、离子、中性原子、激发态原子、光子和自由基等组成，但整体表现出电态原子、光子和自由基等组成，但整体表现出电中性。中性。 等离子体又称物质第四态，它是包含足够多的正等离子体又称物质第四态，它是包含足够多的正负电荷数目近于相等的带电粒子的非凝聚系统。负电荷数目近于相等的带电粒子的非凝聚系统。 What is PLASMA?

2、“Fourth State” of matter Ionized gas at high temperature capable of conducting electrical current Lightning is an example from nature等离子体催化等离子体催化 等离子体催化净化技术是利用高能电子射线激活、等离子体催化净化技术是利用高能电子射线激活、电离、裂解废气中各组分，从而使其发生一系列复电离、裂解废气中各组分，从而使其发生一系列复杂的物理变化和化学反应，而随后的催化剂将促进杂的物理变化和化学反应，而随后的催化剂将促进副产物的转化，并降低反应的活化能，把有害物转

3、副产物的转化，并降低反应的活化能，把有害物转化为无害的或有用的物质加以回收。化为无害的或有用的物质加以回收。 低温等离子体催化技术解决了传统的净化方法所不低温等离子体催化技术解决了传统的净化方法所不能解决的问题。能解决的问题。利用该技术来处理废气始于利用该技术来处理废气始于2020世纪世纪7070年代，有的已进入应用阶段。低温等离子体催化年代，有的已进入应用阶段。低温等离子体催化可以处理废气，如可以处理废气，如VOCsVOCs，还原脱硫、联合脱硝等。，还原脱硫、联合脱硝等。 When an electric field is applied to a volume of gas, highly

4、 energetic electrons are generated.Highly energetic electrons rapidly collide with gas molecules initiating a succession of chemical reactions. Active plasma species is formed, including free radicals, ions, excited molecules.In the case of a plasma formed in a mixture of methane and carbon dioxide,

5、 new gas molecules such as H2 is formed.Dry: CH4 + CO2 = 2CO + 2H2With water: CH4 + 2H2O = CO2 + 4H2Applied Catalysis B: Environmental 94 (2010) 1926 Prepr. Pap.-Am. Chem. Soc., Div. Fuel Chem. 2004, 49 (1), 180Processes of plasma Non-thermal Plasmas Electrical Properties & ChemistryElectrical p

6、ropertiesn Depending on reactor typen Pulsed corona large volume/surface ratio, large discharge gapn Dielectric barrier large surface/volume ratio, small discharge gap; barrier properties; frequency (capacitive coupling)n Dielectric packed bed intermediate surface/volume ratio & discharge gap; d

7、ielectric packed be properties; frequency (local capacitive coupling)Chemistryn Fast radical & ion formation (E/n) in active discharge regionn Pulsed corona streamer headn Dielectric barrier -discharges; ionization waves; fully developed streamers; Atmospheric Pressure Glow Dischargen Slow volum

8、e chemistry (chain reactions) Plasma-Catalytic Reactor Concepts1-stage reactor (plasma in contact to catalytic surfaces) Example: DPB reactorn Dielectric properties of catalyst need to fit to application n Direct interaction of plasma & catalyst enabled2-stage reactor (no direct plasmacatalyst c

9、ontact) Example: DBD & catalystn electrical conductivity of the catalyst doesnt play a rolen catalytic reactions initiated e.g. by metastable intermediate productsPlasma Activation of Catalytic ReactionsPhysical/chemical effectsGas heatingCatalyst heatingElectric fieldsVibrational excitationDiss

10、ociationIonizationUV radiationIntermediate product formationApplication of plasma catalysisCatalyticNOXremovalCatalytic methane conversionCatalytic VOCs degradationCatalytic CO2 reductionCatalyst preparation, regenerationPlasmaPlasma-Catalytic Hybrid Processes for Gas CleaningPlasma induced/enhanced

11、 selective catalytic NOx-reduction for automotive exhaust gases (SAG, Ford, Chrysler, LLNL, PNNL, .) n oxidation due to dielectric barrier discharge (DBD) pretreatmentn non-precious metal catalyst & urea / fuel as a reducing agent NOx-reduction in an oxidizing atmosphere catalytic activity exten

12、ded to low temperatures sulfur tolerant Plasma assisted catalytic oxidation of VOCs for the decontamination of ground water of industrial sites (IUT)n extraction of VOCs from ground water by air stripping: large gas flows, low gas temperaturen efficient plasma pre-treatment using dielectric barrier

13、discharges catalytic oxidation of the VOCs at low temperature (100 C)Sorption & plasma assisted oxidation of VOCs using oxygen plasma (AIST)n Sorption of VOC from off-gasn Regeneration of catalytic sorbent by oxygen plasma Increased efficiency compared to direct plasma-catalytic conversionCH4 +

14、CO2 = 2CO + 2H2Fig. Plasma reactor.1 gas inlet2 high voltage electrode3 discharge gap 4 electric heater5 grounded electrode6 gas outletThe reagent activation by electron impact or by reactions with atomic and molecular active species:CH4 + e = CH3 + H + eCH4 + e = CH2 + H2 + eCH4 + e = CH + H2 + H +

15、 eCO2 + e = CO + O + eFast homogeneous reactions proceed in the gas phase between the short living active speciesReactions induced by the solid surfaces take place on electrode surfaces and inside the discharge volume. Three stages of Plasma catalytic reactionApplied Catalysis B: Environmental 94 (2

16、010) 1926 Application of plasma catalysisApplication of plasma catalysis Plasma catalytic hybrid processes can successfully be applied for the abatement of odorous & noxious compounds from off-gaseso Hybrid processes were demonstrated (Plasma enhanced selective catalytic NOx reduction; Plasma en

17、hanced catalytic oxidation of HCs & VOCs) Good energy efficiency, low operation costs can be expected. Plasma-catalytic hybrid reactor & power supply concepts are available Sorption properties of catalyst are importanto Catalyst needs to be tailored for application (intermediate product gene

18、rated by plasma, plasma regeneration of catalyst, .)Application of plasma catalysisElectron collision dissociation of oxygen Radical attack of HCs Oxidation of NO NO-Reductione + O2 e + O + OO + C2H4 HCO + CH3 + HCH3 + O2 CH3O2H + O2 HO2RO2 + NO NO2 + ROO + NO + M NO2 + M O + NO2 NO + O2NO + N N2 +

19、OO2 + N NO + OAdvantages and shortcomings of plasma catalysis等离子体催化技术的优点等离子体催化技术的优点用该项技术处理有机废气具有以下优点：用该项技术处理有机废气具有以下优点：能耗低，可在室温下与催化剂反应，无需加热能耗低，可在室温下与催化剂反应，无需加热, ,极大地节约了能源极大地节约了能源; ;使用便利，设计时可以根据风量变化以及现场条使用便利，设计时可以根据风量变化以及现场条件进行调节；件进行调节；不产生副产物，催化剂可选择性地降解等离子体不产生副产物，催化剂可选择性地降解等离子体反应中所产生的副产物；反应中所产生的副产物；不

20、产生放射物不产生放射物; ;1.1. 尤其适于处理有气味及低浓度大风量的气体。尤其适于处理有气味及低浓度大风量的气体。CatalystCatalysis Today, 2002, 72: 173184A good catalyst must have certain characteristics: provide a sufficiently high reaction rate under the specific reactive conditions; sustain its activity over a long period of time; exhibit low sensit

21、ivity to poisons, such as sulfur compounds; have good mechanical strength; show selectivity, it should accelerate the desired reaction only; be reduced before use since most of catalysts are produced as oxides. The reduction period should be as short as possible in order to avoid a decrease in the p

22、roduction efficiency.等离子体催化中的催化剂等离子体催化中的催化剂 等离子体催化净化技术采用的催化剂包括等离子体催化净化技术采用的催化剂包括几类：铁电体材料；分子筛；贵金属催化几类：铁电体材料；分子筛；贵金属催化剂；金属氧化物及其金属盐催化剂；光催剂；金属氧化物及其金属盐催化剂；光催化剂；多性能颗粒混合物等。化剂；多性能颗粒混合物等。Catalyst preparationCatalysis Today, 2002, 72: 173184Main trends: plasma chemical synthesis of ultrafine particle catalyst

23、s; plasma assisted deposition of catalytically active compounds on various carriers, especially plasma spraying for the preparation of supported catalysts; plasma enhanced preparation or plasma modification of catalysts. Advantages: a highly distributed active species; reduced energy requirements; e

24、nhanced catalyst activation, selectivity, and lifetime; (1)shortened preparation time.Catalyst preparation, regenerationv Plasma-chemical synthesis and regeneration of catalysts Catalysis Today, 2002, 72: 2132211: electric-arc dc plasmatron; 1a: thoriated tungsten cathode; 1b: copper water-cooled an

25、ode; 1c: plastic adjusting ring; 2: CW PCR; 3: quenching device; 4: copper water-cooled sections for the quenching device; 5: powder-trapping chamber; 6: filter; 7: vibration powder-feeding; 8: current rectifier; 9: flow-meters; 10: bottles with plasma-forming, powder carrying and quenching gases; T

26、1: temperature of inlet water; T2: temperature of outlet water.Schematic drawing of the plasma-chemical installation for synthesis and regeneration of catalysts.Catalyst preparation, regenerationv Plasma-chemical synthesis and regeneration of catalysts Catalysis Today, 2002, 72: 213221Electron micro

27、scope photograph of samplespherical in shapeequivalent diameters fell within the range of 1030 nmv Plasma-chemical synthesis is effective for regenerating spent industrial catalysts.Catalysis Today, 2002, 72: 173184(a) glow discharge; (b) microwave plasma; (c) plasma spraying.Schematically represent

28、atives of electrode configurations of discharge phenomena applied for catalyst preparationDevices for catalyst preparationCommercial Plasma TorchPlasma torch in operationPlasma assisted deposition of catalytically active compounds on various supportsCatalysis Today, 2002, 72: 173184CatalystPlasmaMet

29、al and metal oxides of Fe, Ni, Cr, Cu, Au: supported on a supportsPlasma platingFeCr or FeCrNi/supportPlasma sprayed alloyCo and Cu oxides on Al2O3 fiber sheetPlasma vapor depositionPt supported on porous NiCr alloyThermal plasma sprayingDual-layer ceramic coated surfacePlasma depositionHoney Pt sup

30、port plasma, coated with PdPlasma depositionCatalyst for combustion (Pt, Au)Plasma spraying on a metal support-Al2O3 and -Al2O3 supported on Ni, Ti, CoLaElectric-arc plasma torchNi catalyst for hydro-treatingHigh frequency plasmaCoFePlasma sprayingTable . Illustrative catalysts prepared using plasma

31、 sprayingCatalysis Today, 2002, 72: 173184Thermal plasmaCold plasmaPressureAtmospheric or higherLow (0.1 bar) for most casesAppearanceFilamentary inhomogeneousHomogeneousTemperaturesHigh electron temperatureHigh electron temperatureHigh gas (bulk) temperatureLow gas temperatureDe-excitation rate in

32、gas phaseHighLowTypesPlasma jet; dc corona torch; arcGlow; radio frequency; microwaveUsesUltra-fine particles spraying; sputteringModification or treatment of catalyst surfaceTable . Characteristics of thermal and cold plasmas used for catalyst preparationCatalyst regenerationv Surface of Catalyst t

33、reated by discharge plasma Catalysis Today, 2006, 115: 205210The schematic representative of setup for glow discharge catalyst treatment.Catalyst regenerationv Surface of Catalyst treated by discharge plasma Catalysis Today, 2006, 115: 205210 The catalyst prepared by plasma treatment shows an improv

34、ed low-temperature activity and an enhanced stability. Compared to the reported work, methane conversion over the plasma treated catalyst has a ca. 20% increase at the same reaction temperature. The plasma treated catalyst possesses a better anti-carbon deposit performance for carbon dioxide reforming of methane, compared to the reported work. The plasma treatment followed by calcination thermally induces a generation of specific nickel particles on the support. H